Mechanical Consequences of Molecular Composition on Failure in Polyolefin Composites Containing Glassy, Elastomeric, and Semicrystalline Components
- UMM
In order to gain insights into the mechanisms of deformation and ultimate failure in a homologous series of lamellae-forming polyolefin block copolymers comprised of glassy poly(cyclohexylethylene) (C), elastomeric poly(ethylene-alt-propylene) (P), and semicrystalline poly(ethylene) (E), the anisotropic tensile properties of samples in which the microphase separate structure is oriented on a macroscopic length scale were probed. Reciprocating shear processing of monodisperse CPCPC and CPEPC-{xi} polymers having mass fraction w{sub c} 0.39--0.44 and 0 {<=} {xi} {<=} 1, where {xi} = w{sub E}/(w{sub E} + w{sub P}), produces 'single-grain' polymer samples with perpendicular-oriented lamellae. Tensile deformation studies in which the strain axis coincides with the lamellar normal direction yield varied mechanical responses ranging from brittle fracture for CEC ({xi} = 0) to ductile behavior for CPEPC ({xi} > 0) and CPCPC. Tandem small- and wide-angle X-ray scattering analysis of samples undergoing deformation shows that application of strain along the lamellar normal in the CPEPC materials results in formation of a folded lamellar structure or 'chevron' morpohology within which the E crystals cant relative to the strain direction. Since the ultimate failure mechanism for materials strained in this direction is chain pullout in the glassy domains, a simple mechanical model applied to the data enables quantitation of the stress required for chain pullout at {approx}4 MPa. Additionally, the mechanical properties of miscible blends of CEC and CPC polymers with matched segregation strengths are shown to mimic those of the covalently linked CPEPC pentablock copolymer.
- Research Organization:
- Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1006754
- Journal Information:
- Macromolecules, Journal Name: Macromolecules Journal Issue: (4) ; 2008 Vol. 41
- Country of Publication:
- United States
- Language:
- ENGLISH
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